The present invention relates to a thrust reverser for a gas turbine engine and in particular a thrust reverser in combination with a fan casing for reducing nacelle and pylon lengths.
Some conventional turbo fan engines have accessories, such as a gearbox, mounted on a rear fan casing and within a surrounding nacelle. The nacelle comprises a thrust reverser unit, which includes an array of cascade boxes, and a bypass exhaust nozzle. The cascade boxes are mounted rearwardly of the rear fan casing and together with a translating cowl of the thrust reverser, mean the nacelle is particularly long. In turn a pylon, attaching the engine to the aircraft, is required to extend a long way forward to support the engine particularly at its front mounting point. One conventional front mount is located on the fan casing adjacent an array of outlet guide vanes, themselves position forward of the rear fan casing. As well as the outlet guide vanes supporting the fan casing a pair of A-frames spans between the rear fan casing and a core engine.
The axial position of this conventional thrust reverser unit is determined by the rear fan casing configuration, which is itself determined by (a) the size and number of engine accessories (e.g. gearbox and generator), (b) the position of the gearbox's radial drive and (c) a required location for the A-frames to attach to and react loads onto a suitably rigid core engine structure.
Since the axial location of the bypass exhaust nozzle is critical to engine placement on an aircraft's wing, this conventional engine is relatively far forward. This results in a long pylon with associated high over hung engine loads, increased weight and aerodynamic drag penalties of a long nacelle.
Therefore it is an object of the present invention to reduce the lengths of both the pylon and the nacelle in order to obviate the above mentioned disadvantages.